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Title: EFFICIENT ALLOCATIONS OF IRRIGATION WATER AND NITROGEN FERTILIZER IN CORN PRODUCTION

Author
item Lu, Yao
item Camp Jr, Carl
item Sadler, Edward

Submitted to: Journal of Sustainable Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2004
Publication Date: N/A
Citation: N/A

Interpretive Summary: Water is used in many competing industries and its supply is limited in most irrigation projects. Farmers must compete for use of water on the basis of crop productivity and economic efficiency. Interacting with water, nitrogen fertilizer can increase crop yields and thus improve water use efficiency. To use water and nitrogen fertilizer efficiently in crop production, knowledge about plant responses to nitrogen fertilizer and irrigation water, or production functions, is essential. In this paper, corn production functions were estimated using the data from experimental plots in Florence, South Carolina, U.S.A., from 1999 through 2001. The estimated production functions were then used to determine the optimal levels of water and nitrogen fertilizer applications under the yield-maximizing strategy often used by farmers and the profit-maximizing strategy used by economists. Results indicate that the yield-maximizing strategy called for more water and nitrogen fertilizer and yielded smaller net returns than the profit-maximizing strategy. The results obtained using profit-maximization strategy depend on the relative prices of corn, water, and nitrogen fertilizer. The results provide useful information to extension personnel and corn producers to make nitrogen fertilizer and irrigation decisions for profit maximization and for resource conservation.

Technical Abstract: N-fertilizer and irrigation water are major inputs to corn production and efficient use of these inputs is essential for profit maximization and resource conservation. To use these inputs efficiently, knowledge about plant responses to N-fertilizer and irrigation water, or production functions, is essential. Corn production functions were estimated using the data from experimental plots in Florence, South Carolina, U.S.A., from 1999 through 2001. There were three irrigation treatments and four N-fertilizer regimes. Several forms of production functions were fitted to the data and the quadratic form of the production function was found to have the best fit for the data. The estimated production functions were then used to determine the optimal levels of water and N-fertilizer applications under both yield-maximizing and profit-maximizing strategies. Results indicate that the yield-maximizing strategy called for more water and N-fertilizer and yielded smaller net returns than the profit-maximizing strategy. In 1999, for example, under the current average prices of corn, water, and N-fertilizer, the yield-maximizing strategy required 667 ha-mm of water and 224 kg of N-fertilizer to produce 10.4 Mg/ha of corn and $5.42 of net returns; whereas the profit-maximizing strategy required only 556 ha-mm of water and 174 kg of N-fertilizer to produce 9.87 Mg of corn and $57.38 of net returns. The least-cost combinations of water and N-fertilizer application levels for a given output were also determined. The results provide useful information to farmers to make N-fertilizer and irrigation decisions for profit maximization and for resource conservation.